Retractable mechanisms have been in use for many years for such applications as retractable beds. The retraction mechanisms were supported by a floor assembly and relied on counterbalanced weights and pulley systems to affect load repositioning.
More recently, Brie et al. in U.S. Pat. No. 3,999,245 disclosed a retraction assembly usable for retractable beds and other retractable apparatus which was anchored to the floor or other appropriate support and employed a coil spring and hinge mechanism to provide pivoting of a load such as a bed between a vertical position and a horizontal position.
Coil springs have several limitations and shortcomings. They are built specifically for a given load range and, thus, are not easily modified to accommodate loads significantly heavier or lighter than the spring load rating. In order to handle significantly heavier or lighter loads, a coil spring assembly would require a complete upgrade of the coil spring and its housing. Coil springs also begin to wear and lose part of their original properties such as spring constant, which cannot easily be adjusted. Thus, as a coil spring assembly weakens due to normal use, and no easy method exists to readily compensate for the loss of the original spring properties.
Thus, it appears desirable to design a retraction apparatus for load repositioning which would provide for greater load flexibility and durability. It also appears to be desirable to provide a retraction apparatus that can be easily adjusted with respect to load capacity and with respect to age induced losses of the original spring characteristics. It also appears to be desirable to provide a retraction apparatus which can be incorporated into a retractable bed and which will allow efficient repositioning of an attached load from vertical to horizontal positions and back again.